Agaricus bisporus, commonly known as portobello, is one of the most popular strains of mushroom grown in the United States. The common button and cremini are actually the same strain of brown mushroom, but the gills have not been allowed to open before harvesting. Portobello mushrooms are allowed to mature and harvested later than button or cremini. Agaricus bisporus is a flavorful addition to salads, soups, sauces and stir-fry. Low in calories and high in flavor and nutrients, tasty mushrooms can be easily cultivated by the home gardener.
Order mushroom spawn online or from local mushroom growers. Agaricus bisporus (portobella, cremini and white button mushrooms) grow from microscopic spores, not seeds. Spores are collected in the laboratory and used to inoculate grains or seed to produce a product known as spawn, the gardener’s equivalent of seed. You will require approximately two cups of spawn for a every 6 to 8 feet of growing tray. After you purchase mushroom spawn, you’ll have to create the medium or bed for the mushrooms to grow in.
Prepare a growing media of equal parts organic compost, well-aged herbivore manure (cow, horse, chicken, goat, sheep, llama) and peat moss. Mushrooms obtain all of their required growth nutrients from organic matter in the growing medium.
Grow mushrooms indoors in a growing tray. Trays should be at least 8 inches deep to contain the growing medium. Locate growing trays in a dark room where you can maintain a temperature of between 55 and 70 degrees Fahrenheit.
Fill growing trays to within 2 inches of the lip with moist organic compost. Carefully sprinkle the spores evenly onto the compost and press down firmly. Keep the trays uniformly moist and in the dark until fine white webbing (mycelium) begins to appear on the surface of the growing media.
Cover growing trays with a 1 to 2 inch layer of damp peat moss, topped with a thick layer of damp newspaper. Mist the newspaper daily for 7 to 14 days while maintaining a temperature in the growing room of 55 degrees Fahrenheit. When pinheads of young mushrooms develop, remove the newspaper and raise the temperature to 65 degrees Fahrenheit.
Continue daily misting as the mushrooms mature. Button sized mushroom can be harvested when they are about the size of a dime. If allowed to grow and develop, mushrooms can be harvested at the cremini stage of 2 to 3 inch wide caps. Cremini mushrooms are picked before the gills of the mushroom begin to open. If you wish to harvest portobellos, delay harvesting until the gills of the mushroom open and the caps have developed to 4 to 6 inches in size.
Mushrooms are perishable. To keep them longest, its best to refrigerate them, unwashed. Under refrigeration they will stay fresh seven to ten days. Fresh mushrooms can be broiled, sauteed, grilled, braised, stewed, or deep-fried. A bountiful harvest can be preserved by canning, pickling, drying and grinding the dry mushrooms into powder to add to soups, stews and sauces.
Keep growing medium uniformly moist at all time. If allowed to dry out, mushroom spawn will die.